问题补充：
—What did he say just now?
—He said .
A. what time the library was build.
B. he has made many mistakes in the exam.
C. if the teacher would ask him to go to the office the next day
D. his mother had waited for him for 20 minutes at the school gate.
答案：
A. what time the library was build.
B. he has made many mistakes in the exam.
C. if the teacher would ask him to go to the office the next day
D. his mother had waited for him for 20 minutes at the school gate.
解析：考查宾语从句。句意：刚才他说什么？他说他的妈妈在校门口等了他20分钟。A项用特殊疑问词引导，图书馆什么时候被建，用将来时。B项错在时间，主句是过去时，从句用相应的过去，故用过去完成时。而C项句意表达错误。所以选D项。
